EPW Forum

Hi,

I am having some problems running epw.x for body centered tetragonal NbAs. Every time the calculation gets past the gamma q point I get the following error:

===================================================================
irreducible q point # 1
===================================================================

Symmetries of small group of q: 4
in addition sym. q -> -q+G:

Number of q in the star = 1
List of q in the star:
1 0.000000000 0.000000000 0.000000000
Imposing acoustic sum rule on the dynamical matrix

q( 1 ) = ( 0.0000000 0.0000000 0.0000000 )


===================================================================
irreducible q point # 2
===================================================================

Symmetries of small group of q: 2
in addition sym. q -> -q+G:

Number of q in the star = 2
List of q in the star:
1 0.500000000 0.000000000 -0.147761123
2 -0.500000000 0.000000000 -0.147761123

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Error in routine readmat_shuffle2 (1):
wrong qpoint
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

stopping ...


I have followed the procedure from the tutorial and I'm not sure what is going wrong as the qpoints I am trying to calculate are identical to those output by ph.x. I have tried the calculation using both ibrav=7 and ibrav=0 with specified CELL_PARAMETERS and the same error occurs in both cases. The following are my nscf_epw, and epw input files for the each part of a very basic version of the calculation (not converged). I have used a kpoint grid of 4X4X4 and a qpoint grid of 2X2X2. Any insight into this issue would be much appreciated.
################
nscf_epw.in

&control
calculation = 'nscf'
prefix = 'NbAs'
wf_collect =.true.
pseudo_dir = '../'
outdir = './'
verbosity = 'high'
/
&system
! ibrav = 7
ibrav = 0
celldm(1) = 6.52276767
! celldm(2) = 1
! celldm(3) = 3.38383985
nat = 4
ntyp = 2
ecutwfc = 40
occupations = 'smearing'
smearing = 'm-v'
degauss = 0.02
!nbnd = 40
lspinorb = .true.
noncolin = .true.
nosym = .true.
/
&electrons
diagonalization = 'david'
mixing_beta = 0.7
conv_thr = 1.0d-10
/
ATOMIC_SPECIES
Nb 92.90638 Nb.UPF
As 74.92 As.UPF
CELL_PARAMETERS {alat=6.52276767}
0.500000 -0.500000 1.691920
0.500000 0.500000 1.691920
-0.500000 -0.500000 1.691920
ATOMIC_POSITIONS {angstroms}
Nb 0.00000 1.72585 2.92000
Nb 0.00000 0.00000 0.00000
As 0.00000 1.72585 7.77888
As 0.00000 0.00000 4.85888
K_POINTS crystal
8
0.00000000 0.00000000 0.00000000 0.1250000
0.00000000 0.00000000 0.50000000 0.1250000
0.00000000 0.50000000 0.00000000 0.1250000
0.00000000 0.50000000 0.50000000 0.1250000
0.50000000 0.00000000 0.00000000 0.1250000
0.50000000 0.00000000 0.50000000 0.1250000
0.50000000 0.50000000 0.00000000 0.1250000
0.50000000 0.50000000 0.50000000 0.1250000

#######################
epw.in

--
&inputepw
prefix = 'NbAs'
amass(1) = 92.90638
amass(2) = 74.92
outdir = './'

iverbosity = 3

elph = .true.
epbwrite = .true.
epbread = .false.

etf_mem = 0

epwwrite = .true.
epwread = .false.

nbndsub = 18
nbndskip = 6

wannierize = .true.
num_iter = 300
dis_win_max = 21
dis_win_min = -3
dis_froz_min= -3
dis_froz_max= 13.5
proj(1) = 'random'

elecselfen = .true.
nest_fn = .false.
phonselfen = .false.
a2f = .false.

specfun_el = .true.
wmin_specfun = -4
wmax_specfun = 1
nw_specfun = 20

parallel_k = .true.
parallel_q = .false.

fsthick = 2 ! eV
eptemp = 300 ! K
degaussw = 0.30 ! eV

dvscf_dir = './save/'

nkf1 = 4
nkf2 = 4
nkf3 = 4

nqf1 = 4
nqf2 = 4
nqf3 = 4

nk1 = 2
nk2 = 2
nk3 = 2

nq1 = 2
nq2 = 2
nq3 = 2
/
4 cartesian
0.000000000 0.000000000 0.000000000
0.500000000 0.000000000 -0.147761123
0.500000000 -0.500000000 -0.295522247
0.000000000 0.000000000 -0.295522247

Hello,

Your q-point list in epw.in should be exactly the same as the one used to create the dvscf from the phonon run.

Therefore make sure the output of ph.x is the same as

0.000000000 0.000000000 0.000000000
0.500000000 0.000000000 -0.147761123
0.500000000 -0.500000000 -0.295522247
0.000000000 0.000000000 -0.295522247

You might possibly not have enough digits.

Also, are you sure all the z-direction values are negative ?

Hi sponce,
Thank you for your quick reply.

I copied the q-point list from the output of the phonon run. I also tried to run epw.x after extending the digits of the q-point coordinates to match those in the dyn files exactly so that they read

4 cartesian
0.0000000000000000 0.0000000000000000 0.0000000000000000
0.5000000000000000 0.0000000000000000 -0.1477611234573739
0.5000000000000000 -0.5000000000000000 -0.2955222469147478
0.0000000000000000 0.0000000000000000 -0.2955222469147478.

However, is till get the same error when I run epw.x.

I am reasonably confident that these are the correct q-points. The corresponding 4X4X4 k-points from the scf run (with the matching 2X2X2 q-point in blue) are

cart. coord. in units 2pi/alat
k( 1) = ( 0.0000000 0.0000000 0.0000000), wk = 0.0156250
k( 2) = ( -0.2500000 0.0000000 0.0738806), wk = 0.1250000
k( 3) = ( 0.5000000 0.0000000 -0.1477611), wk = 0.0625000
k( 4) = ( -0.2500000 0.2500000 0.1477611), wk = 0.1250000
k( 5) = ( 0.5000000 0.2500000 -0.0738806), wk = 0.2500000
k( 6) = ( 0.2500000 0.2500000 0.0000000), wk = 0.0625000
k( 7) = ( 0.5000000 -0.5000000 -0.2955222), wk = 0.0312500
k( 8) = ( 0.0000000 0.0000000 0.1477611), wk = 0.0312500
k( 9) = ( 0.7500000 0.0000000 -0.0738806), wk = 0.1250000
k( 10) = ( 0.5000000 0.0000000 0.0000000), wk = 0.0625000
k( 11) = ( 0.7500000 -0.7500000 -0.2955222), wk = 0.0625000
k( 12) = ( 0.5000000 -0.5000000 -0.1477611), wk = 0.0312500
k( 13) = ( 0.0000000 0.0000000 -0.2955222), wk = 0.0156250.

Is it possible I have the units of the q-point coordinates incorrect?

Thanks again for your help.

Hello,

From the nscf input that you posted, I see:

ibrav = 0
celldm(1) = 6.52276767
CELL_PARAMETERS {alat=6.52276767}
0.500000 -0.500000 1.691920
0.500000 0.500000 1.691920
-0.500000 -0.500000 1.691920
ATOMIC_POSITIONS {angstroms}
Nb 0.00000 1.72585 2.92000
Nb 0.00000 0.00000 0.00000
As 0.00000 1.72585 7.77888
As 0.00000 0.00000 4.85888

It might be correct, but to me is look suspicious that you have negative "z" for your q-point grid from phonon. From your input the grid should be only positive in z I guess.

Best wishes,
Samuel

Dear Dr. Samuel Ponc
I am facing a problem in running epw.x executable. I am exactly following one of your examples "Resistivity and mobility with EPW
Tutorial Wed.5 Hands-on session" The first three steps are running smoothly but when I run the epw.x command, I am getting the following error


Program EPW v.5.0.0 starts on 8Sep2018 at 16:43:12

This program is part of the open-source Quantum ESPRESSO suite
for quantum simulation of materials; please cite
"P. Giannozzi et al., J. Phys.:Condens. Matter 21 395502 (2009);
"P. Giannozzi et al., J. Phys.:Condens. Matter 29 465901 (2017);
URL http://www.quantum-espresso.org",
in publications or presentations arising from this work. More details at
http://www.quantum-espresso.org/quote

Parallel version (MPI), running on 2 processors

MPI processes distributed on 1 nodes
K-points division: npool = 2

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Error in routine epw_readin (5010):
reading input_epw namelist
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

stopping ...
--------------------------------------------------------------------------
MPI_ABORT was invoked on rank 0 in communicator MPI_COMM_WORLD
with errorcode 1.

Hello,

The tutorial was done with an prior version of EPW.

In the latest version 5 of EPW, the following two input variables have been removed:

parallel_k = .true.
parallel_q = .false.

Just remove them from the input and it should work.

Best,
Samuel

Thank you.
By removing the two lines in the input file, the code is working now.